1. Field of the Invention
The invention relates to an amplifier, and more particularly to a class AB amplifier.
2. Description of the Related Art
Power amplifiers comprise class A amplifiers, class B amplifiers, class C amplifiers, and class AB amplifiers according to different work points. Class A amplifiers comprise the best signal transmission property (the waveform is not distorted). When a class A amplifier does not receive an input signal, current is continuously provided from an output terminal thereof. Thus, a power efficiency range of the class A amplifier is between 20% to 30%. Power efficiency of a class B amplifier can reach 75%. In output waveform output from the class B amplifier, the output waveform is distorted in a positive half cycle or a negative half-cycle. Thus, an input waveform can not be completely amplified.
A class AB amplifier benefits from the advantages of the class A amplifier and the class B amplifier. Power efficiency of the class AB amplifier exceeds that of the class A amplifier.